1. Field of the Invention
The invention relates to a multilayer printed board compound as well as a method for the manufacture thereof and for the manufacture of planar transformers and planar coils on the basis of the multilayer printed board compounds.
2. Background Art
Multilayer printed board compounds have been known for some time under the designation xe2x80x9cmultilayerxe2x80x9d. In this case, several layers of printed circuit board are disposed one above the other and joined to each other by so-called xe2x80x9cprepregsxe2x80x9d. The typical thickness of the base circuit pathsxe2x80x94also referred to as conducting pathsxe2x80x94used herein, which are structured by photographic engraving techniques, is in the range of approximately 18 xcexcm to 70 xcexcm so that the recesses between the circuit paths are filled with resin that emerges from the prepregs upon pressing. Owing to developments in automotive industry, the energy demand for current supply in the vehicle has increased, requiring novel high performance power units. Owing to restricted conductivity, the known printed board systems, which have copper circuit paths of 18xcexc to 70 xcexcm of thickness, are not sufficient in the case of high frequency currents. Therefore, printed boards have been developed, the circuit paths of which have a thickness of 400 xcexcm. Printed boards of this type cannot be connected with each other planely by the methods existing so far, since the resin that emerges from the prepregs upon pressing is not sufficient for completely filling the recesses between the printed boards and keeping the given total thicknesses of the multilayer printed boards. In particular in the case of thermal strains, this may result in delamination of the multilayer printed boards. Furthermore, arc-over voltage will occur between the circuit paths of a printed board and the circuit paths of neighboring printed boards, there being no uniform insulation by resin.
It is an object of the invention to embody a multilayer printed board compound as well as a method for the manufacture thereof, in which the individual printed circuit boards are durably and regularly joined to each other.
This object is attained in a multilayer printed board compound, comprising at least two printed boards, which are disposed planely one above the other and each of which comprises an electrically insulating mother board, electrically conductive circuit paths, which are provided on at least one side of the mother board, and recesses, which are defined laterally by the circuit paths and towards the mother board by the mother board; and further comprising at least one preimpregnated board disposed between the printed boards for joining the printed boards; wherein the recesses, which are disposed between the mother boards of the respective printed boards, are substantially completely filled with a synthetic resin paste; and wherein the at least two printed boards and the at least one preimpregnated board are joined by pressing. Furthermore, this object is attained by a method for the manufacture of a multilayer printed board compound, comprising the following steps: at least two printed boards are provided, each of which comprising an electrically insulating mother board, electrically conductive circuit paths, which are provided on at least one side of the mother board, and recesses, which are defined laterally by the circuit paths and towards the mother board by the mother board; the recesses of the printed boards are substantially completely filled; at least one preimpregnated board is applied to a first printed board; a second printed board is applied to the preimpregnated board; and the at least two printed boards and the at least one preimpregnated board are joined by pressing.
Additional features and details will become apparent from the description of five exemplary embodiments, taken in conjunction with the drawing.